The present invention relates to a motor-driven compressor having a compression mechanism, an electric motor, and a motor drive circuit which are disposed along the axial direction of a drive shaft of the compressor.
Such a motor-driven compressor used for a vehicle air conditioner or the like is disclosed in, for example, Japanese Patent Application Publication No. 2004-324494. The outer shell of the motor-driven compressor disclosed in the above reference includes a main housing and a front housing. The main housing is made of an aluminum alloy and formed in a cylindrical shape. The front housing is formed in the shape of a cover and connected to the front end of the main housing. The main housing of the motor-driven compressor accommodates therein an electric motor substantially at the center, a compression mechanism in the front, and a motor drive circuit in the rear. The electric motor has a stator fixed to the inner peripheral surface of the housing and a rotor mounted on the drive shaft inside of the stator. The compression mechanism is fixed to the inner peripheral surface of the main housing, and mounted on the drive shaft which is driven to rotate by the electric motor.
The motor-driven compressor is formed integrally at each of the top and bottom of its outer periphery with a pair of mounting lugs for mounting the motor-driven compressor on a vehicle engine (an object to which the motor-driven compressor is to be mounted). Specifically, the mounting lugs of each pair are spaced in the axial direction of the housing. Bolts (fastening members) are inserted through holes formed through the mounting lugs and screwed into bosses extending from the vehicle engine, so that the motor-driven compressor is mounted on the vehicle engine.
In the motor-driven compressor disclosed in the above reference, the mounting lugs of the main housing is formed at positions outside of the compression mechanism and the electric motor along the axial direction of the main housing. Since the mounting lugs are formed integrally with the main housing, the main housing may be deformed due to differences of the clamping forces of the bolts, poor dimensional accuracy of the bosses, and the like when the mounting lugs are fastened to the bosses by the bolts. As a result, the compression mechanism and the electric motor fixed to the main housing may be displaced out of alignment, and the rotary shaft is displaced out of axial alignment. This causes unwanted noise and deterioration of the durability of bearings supporting the rotary shaft.
The present invention is directed to providing a motor-driven compressor in which a first housing (main housing) can be prevented from being deformed by fastening of the mounting lugs to an object to which the motor-driven compressor is to be mounted by means of fastening members.